Human lung mast cell tryptase, a trypsin-like serine proteinase, is a major component of mast cells. Tryptase exists are as a 135 kDa tetramer, with active subunits of 30.9 and 31.6 kDa. The two subunits or isozymic forms have been isolated from human lung tissue and these glycoproteins will be deglycosylated to determine whether their differences are due to glycosylation. Additionally, these two isozymic forms of tryptase will be compared by peptide mapping and amino acid sequence analysis to see if they differ in primary structure. Studies using synthetic substrates and inhibitors will provide comparative data for the two forms of tryptase and active site data in comparison with other trypsin-like enzymes. High molecular weight kininogen is a cofactor for contact activated coagulation and one of the few known natural substrates of tryptase. Therefore, the site at which tryptase cleaves this protein and inactivates it as a coagulation component will be determined by amino acid sequence analysis of isolated fragments. The affinity of tryptase for heparin and the effect of heparin on enzyme activity and specificity will be investigated. Various tissues will be examined for tryptase and inhibitors of tryptase. Blood leukocytes have been found to contain proteins which are immunologically similar to lung tryptase and these will be purified for comparison with mast cell tryptase. These studies should result in better methods for distinguishing between mucosal mast cells, connective tissue mast cells and blood basophils, while providing data potentially useful in the study of diseases involving mast cell activation.